Activator precursors for stabilizers for photographic images



United States Patent once 3,531,285 Patented Sept. 29, 1970 US. Cl. 9661 14 Claims ABSTRACT OF THE DISCLOSURE Activator precursors for photographic silver halide elements containing a stabilizer precursor which causes stablization of silver halide by substantially dry processing.

This application is a continuation-in-part of application Ser. No. 371,124, now US. Pat. No. 3,301,678, filed May 28, 1964, to Wilbert J. Humphlett, Dee L. Johnson and Grant M. Haist.

The present invention relates to a substantially dry method and composition containing an activator precursor for stabilization of photographic elements containing silver halide. The invention is also directed to a photographic element containing silver halide in a photographic emulsion and, contiguous to said silver halide, a stabilizer precursor, such as a stabilizer precursor which cleaves upon heating forming isothiourea, and a stabilization activator precursor which upon heating cleaves to form moieties which activate or aid in activation or cleavage of the stabilizer precursor.

After an exposed photographc silver halide emulsion is developed and a silver image is produced in exposed areas, a silver halide in the unexposed areas is commonly removed by treatment with sodium thiosulfate or other fixing solutions to produce a soluble silver compound when a permanent silver image is desired. It is possible to fix or stabilize the unexposed and/ or undeveloped silver halide by reaction with a compound which forms a silver salt or complex that is colorless or relatively light in color and resistant to print-out. It is often convenient to incorporate a fixing or stabilizing agent as an integral part of a photographic element. However, commonly used fixing or stabilizing agents are often not suitable for use in layers contiguous to photographic silver halde because they react with the silver halide in unexposed form and render the emulsion useless for photographic purposes.

It has been proposed to add a fixing or stabilizing agent as an integral part of a photographic element which can be readily activated by exposure of the element to elevated temperatures. So-called stabilizer precursor compounds which produce fixing or stabilizing agents under certan conditions have been proposed heretofore. However, many such precursors which may be compatible with silver halide emulsions either cannot be activated at elevated temperatures at which conventional photographic silver halide emulsions can be processed within the desired time limits or they are prematurely activated either at temperatures of conventional use and storage or below which stabilization or fixing is desired.

It has also been proposed to add a precursor compound to a photographic element which upon heating cleaves or decomposes to form alkaline materials which cause an increase in the pH of the element. Such precursors have not been satisfactory heretofore in photographic elements for the same reason that fixing agents or stabilizer precursors have not been satisfactory.

The results of attempts which have been made to produce a photographic element, composition or process for stabilizing photographic images under essentially dry conditions with the aid of heat have not been satisfactory. The components of the element have either caused prestabilization, undesired print-out, excessive fog, or other undesired characteristics Isothiourea derivatives have been proposed as stabilizer precursors in co-pending application, Ser. No. 371,124, filed May 28, 1964 of Humphlett et al., now US. Pat. 3,301,678, the disclosure of which is incorporated herein by reference. Certain isothiourea derivatives, however, have not been found satisfactory due to their undesirable odor. Moreover, it has been found that the time required for stabilization could be improved when such stabilizers are used in combination with stabilization activator precursors of the invention.

The present invention comprises a photographic element comprising a photographic silver halide emulsion, and, contiguous to said silver halide, a stabilizer precursor and a stabilization activator precursor each of which are stable under ambient conditions of storage and which effects stabilization of the element within a short period, typically about 1 to about 8 seconds, at temperatures above about C.

The stabilization precursors which may be employed in the elements, compositions and processes of the invention can be compounds which cleave or break down at elevated temperatures to form a compound, such as isothiourea, which complexes or combines with silver halide in the unexposed areas of the emulsion forming a mercaptide compound which is more stable to light, atmospheric conditions and ambient temperatures than silver halide. Suitable stabilizer precursors include the compounds set out in co-pending U.S. Patent applcaton, Ser. No. 371,124, filed May 28, 1964, of Humphlett et al., now US. Pat. 3,301,678. These include sulfur containing compounds which may be represented by the following structures:

1? -CNH2 X is an anion, such as a sulfonate, bromide, chloride,

hydrochloride or trichloroacetate radical; M and Z are each selected from the group consisting of hydroxy and carboxy radcals; A is a radical selected from the group consisting of a hydroxyl radical and a radical having the formula:

2-hydroxyethylisothiurinium chloride Z-hydroxyethylisothiuronium nitrate 2-hydroxyethylisothiuronium trichloroacetate 2-hydroxyethylisothiuronium bromide 3-hydroxypropylisothouroniurn bromide Z-hydroxyethylisothiuronium formate 2-hydroxyethylisothiuronium perchlorate 2-hydroxyethylisothiuronium perchlorate isothiureido acetic acid 2-isothiureidopropionic acid 3-isothiureidobutyric acid Z-hydroxyethylisothiuronium acetate 2-hydroxyethylisothiuronium N- (p-hydroxyphenyl aminoacetate ,8- 2-morpholinoethylthio B-phenyl pro piophenone hydrochloride ,8-(Z-diethylaminoethylthio)-/3-phenylpropiophenone hydrochloride fl- 3-diethylamino-2-hydroxypropylthio -fl-phenyl-pmethoxypropiophenone hydrochloride ,8-Caroxymethylthio-fi-phenylpropiophenone methyl a-carbomethoxy-B- 2-morpholinoethylthio) #3- phenylpropionate hydrochloride Methyl wcarbomethoxy-B-(2-rnorpholinoethylthioH3- (p-methoxyphenyl) propionate hydrochloride Ethyl ot-carbethoxy-fl-(2-morpholinoethylthio phenyl propionate hydrochloride Ethyl ot-carbethoxy-fl(2-rnorpholinoethylthio propionate hydrochloride Z-ethylaminoethylisothiuronium chloride 2-dimethylaminoethylisothiuronium chloride hydrochloride 2hydroxypropylisothiuronium trichloroacetate l,Z-ethylenebis(isothiuronium bromide) N-butylcarbamoyloxyethylisothiuronium chloride a-NitrilO-[M2-rnorpholinoethylthio)-fl-phenylpropionitrile hydrochloride ot-Nitrilo-fi-(2-morpholinoethylthio)propionitrile hydrochloride a-Carbethoxy-fl-(2-morpholinoethylthio)-,8-

phenylp-ropionitrile hydrochloride a-Carbethoxy-fi-(2-morpholinoethylthio propionitrile hydrochloride Ethyl-a-amido-fi-(2-morpholinoethylthio)-5- phenylpropionate hydrochloride Ethyl a-amido'fi-(-Z-morpholinoethylthio) propionate hydrochloride Ethyl a-carbethoxy-fi-(Z-piperidinoethylthio)-B- phenylpropionate hydrochloride Ethyl a-carbethoxy-fi(2-morpholinoethylthio)- propionate hydrochloride Methyl a-carbomethoxy-B-(Z-morpholinoethylthio)- propionate hydrochloride Methyl ot-carbomethoxy-fi-(3-diethylamino-2- hydroxypropylmercapto)-;i-phenylpropionate hydrochloride Methyl a-carbomethoxy-fi-(3-diethylamino-2- hydroxypropylmercapto)-5-phenylpropionate Z-hydroxyethyll -methyli-sothiuronium chloride 2hydroxyethyll,3-dimethylisothiuronium chloride Z-hydroxyethyll -phenylisothiuronium chloride 1-phenyl-2-isothiureidoacetic acid 1-rnethyl-2-isothiureidoacetic acid 2-phenylaminoethylisothiuronium chloride hydrochloride Z-aminoethylisothiuronium chloride hydrochloride l,2-ethylenebis( l-methylisothiuronium perchlorate) 1,2-ethylenebis( l-phenylisothiuronium perchlorate) Carbamyloxyethylisothiuronium chloride N-phenylcarbamoyloxyethylisothiuronium chloride Ethyl-wcarbethoXy-fi-(2-morpholinoethylthio)butyrate hydrochloride.

Other suitable stabilizer precursors include those within the scope of the US. Pat. 3,220,839-Herz and Kalenda. These include isothiourea derivatives represented by the general structures:

wherein R R and R can be hydrogen atoms or hydro carbon radicals, such as aryl radicals, including phenyl radicals, and alkyl radicals, such as lower alkyl radicals, typically those having from 1 to about 5 carbon atoms; R and R can also be acyl radicals having the formula:

ll R5C- wherein R is an alkyl such as those having from 1 to 5 carbon atoms; R, is an alkylene radical or substituted alkylene radical, such as a lower alkyl or phenyl subsituted alkylene radical; Y is an anion, or acid radical such as SO H,, which may form a so-called inner acid salt. Suitable compounds within the scope of this structure include, for example, 2-S-thiuronium ethane sulfanate:

I-IN

CS-CH2GH2SO3H HzN 3-S-thiuronium propane sulfonate:

C-S(CH2)3SO31I HzN 4-S-isothiuronium butane sulfonate:

I'IN

C-S(CH2)4-SO3II H2N 3-S-isothiuronium-l-methyl-propane sulfonate:

HN CI-Ia CSCH2CH2 HSO3I-I HzN The above compounds which contain a sulfonate radical and form so-called inner acid salts are preferred stabilizer precursors. It has been found that these compounds have unexpected properties of being free of obnoxious odors when employed in the elements of the invention. Inner acid salts as employed herein are defined in US. Pat. 3,220,839-Herz and Kalenda.

The term stabilization activator precursor as employed herein refers to those precursors which upon heating in combination with stabilization precursors, such as those set out above, are heat cleavable at temperatures above about C. and which aid in the cleaving or break down of the stabilizer precursor to form mercaptides which complex with silver halide in non-latent image form. Such stabilization activator precursors include those which are stable at temperatures normally encountered during conditions of storage and which in combination with the described stabilizer precursors cause the element with which they are contacted or with which they are present to be light insensitive or resistant to changes in density at temperatures employed in the substantially dry heat processing of the element in a short period, usually less than about 8 seconds.

While some compounds including certain quaternary ammonium bases and other amino compounds will decompose at temperatures employed in the present process, it will be appreciated that certain of these compounds are not activator precursors as employed herein and are not satisfactory for photographic purposes. As indicated in US. Pat. 3,220,839, certain of such compounds provide unpredictable properties to photographic elements and processes. For instance, it has been found that all quaternary ammonium bases do not provide the desired activation of stabilizer precursors in a process for stabilizing a photographic element using a heating means within the required time limits and within feasible concentration ranges in the absence of undesired prestabilization or premature print-out.

Examples of classes of stabilization activator precursors within the scope of the present invention include guanidinium salts, such as diguauidinium glutarate, succinate, malonate, adipate, pimelate or itaconate and monoguanidinium malonate, succinate or trichloroacetate.

Quaternary ammonium malonates, such as piperazinium malonate, piperidinium malonate, pyrrolidine malonate, N,N-diethylenediamine bismalonate, and N-isopropylcyclohexylamine malonate; amino acids such as 4-aminobutyric acid, 6-aminocaproic acid, glycine and DL-serine and certain heat cleavable hydrazide compounds having cleavable nitrogen to nitrogen bonds, such as benzhydrazide, isonicotinic acid hydrazide and N-methyl pipericlinebenzimide have been found suitable. Other compounds which have been found suitable include certain oxazoliclones, including oxazolidone and N-methyl oxazolidone.

Certain heat cleavable quaternary ammonium compounds which provide the desired properties, that is, which are heat activated within the desired time and temperature limitations to activate the stabilizer precursor employed, include certain compounds within the scope of British Pat. 998,949 such as guanidinium trichloroacetate. It will be appreciated, however, that the element, compositions and processes of the present invention are directed to systems containing silver halide and that such systems do not involve the same stabilization mechanisms as are set out in non-silver halide systems, such as diazo systems as decribed in Britih Pat. 998,949.

According to the invention, the stabilizer precursor and stabilization activator precursor combination is activated and causes stabilization within a short period, that is a period of seconds, when the element in which they are present or with which they are contacted is exposed to temperatures of above about 90 C. The temperature range at which the photographic element or composition containing these components are treated will be determined by various components of the emulsion, such as incorporated developing agents and other addenda, as well as the degree of development or stabilization required. Under most conditions, it is desirable to employ temperatures well above 90 C., typically above about 150 C., and usually in the range of about 190 C. to about 260 C. The higher temperatures significantly shorten processing time in most instances to a period of less than about 8 seconds and usually in the range of about 1 to less than about 5 seconds.

Generally heating according to the invention can be carried out by contacting the photographic element containing the stabilizer precursor and stabilization activator precursor with suitable heating means such as metal rolls, infrared radiation, heated plates and the like.

It is usually desirable to elfect the required stabilization within as short a time as possible. According to the invention, the combination of stabilizer precursor and stabilization activator precursor can effectively shorten processing time compared to prior processes such as set out in British Pat. 930,572. The duration of the heating -step within the desired range will be influenced by'such factors as the temperature employed and other addenda present. The optimum heating period can be readily determined considering the temperature, degree of development, suitable stabilization and other factors which can be determined by those skilled in the art.

The concentration of stabilization precursor which is suitable usually is at least about mole of the stabilizer precursor for each mole of silver halide present in the emulsion. Suitable concentrations include about A mole to about 20 moles of the stabilization precursor for each mole of silver halide. However, it is often desirable to use molar excess of the stabilizer precusor to assure effective stabilization of the areas of the silver halide emulsion which are desired to be stabilized. In order to prevent print-out and other adverse effects, such as image obliteration, commonly at least 5 or in certain instances 10 times the required amount of stabilizer precursor can be utilized on a molar basis.

The concentration of stabilization activator precursor will be influenced by the amount of stabilizer precursor employed. In general, the amount of stabilization activator precursor should be sufficient to effect the cleavage or break down of the stabilizer precursor at the temperatures employed. The concentration usually sufficient is about A mole of the activator precursor per mole of silver present in the emulsion as silver halide up to about 20 moles of activator precursor. Typically, about /2 mole of stabilization activator precursor per mole of silver present in the emulsion as silver halide up to about 10 moles of stabilization activator precursor can be employed.

Since certain of the stabilizer precursors can be activated by inorganic alkalis such as alkali metal hydroxides including sodium hydroxide and potassium hydroxide and alkali metal carbonates, such as sodium carbonate, it is usually desirable not to contact the elements containing the combination of precursors of the invention with alka line materials which would cause premature stabilization. For example, in most instances, it would not be desirable to contact a silver halide emulsion containing the stabilizer precursor and stabilization activator precursor with an alkaline aqueous solution of a developer since it would be possible that the stabilization elfect caused by the combination of precursors of the invention would take place before the desired degree of development.

Small amounts of moisture may be present such as the amounts present in conventional photographic paper supports under ordinary conditions such as at 25 C. and 40% relative humidity. Such small amounts of moisture may have a catalytic effect on the cleaving action of the precursor combination and can, accordingly, be useful in the process. Such moisture may be made available during the heating step of the present process.

The term dry as employed herein is intended to include such small amounts of moisture, but is intended to exclude larger amounts of water than are present at ordinary conditions of temperature and humidity. Such larger amounts of water are to be avoided and can have an adverse effect on the compositions and processes of the invention.

The precursor combination of the invention can be employed with various types of photographic emulsions. Suitable emulsions which are useful include orthochromatic, panchromatic, infrared emulsions and X-ray film emulsions; various silver salts may be employed in such emulsions as the photosensitive salt.

The emulsion containing such salts has the silver salt dispersed or suspended in gelatin or other suitable permeable vehicles including polyvinyl alcohol, polyacrylates, acrylic acids and other polymers. Cellulose derivatives such as cellulose esters and ethers may also be employed. Binding agents which are suitable for the precursor combination with photographic elements include polyvinyl alcohol, cellulose acetates and cellulose ethers. Typically, the precursor combination is mixed or otherwise incoporated in a coating composition with the binder and then applied to a suitable support.

It will be appreciated that the precursors may be present in separate layers, in one layer of the element, in the silver halide emulsion layer, in the support, or at various positions of the photographic element. It is necessary, however, that the precursors be contiguous to each other and the silver halide to effect stabilization.

The emulsion, binder, or coating composition utilized in preparing the photographic elements containing the precursor combination can be coated on a wide variety of supports. Typical suitable photographic supports include cellulose ester film and polystyrene film, and related films or resinous materials which will withstand the temperatures employed in heat processing without adversely effecting the desired image or stabilization. Suitable supports also include glass, paper, wood, metal and others employed in the photographic art.

The silver halide elements according to the invention can be sensitized using any of the well known techniques in emulsion making. For example, they may be prepared by digesting with naturally acting gelatin or they may also be sensitized with salts of noble metals. They can also contain speed increasing addenda.

Other addenda which may be included in the photographic element, for example, include suitable antifoggants, plasticizers, toners, coating aids, development restrainers, buffers and hardeners. Sensitizing dyes as well as spectral sensitizers may also be employed.

It is often desirable to incorporate an antimatting agent such as silica with, or contiguous to, the photographic emulsion. The antimatting agent causes the element to be resistant to bonding or sticking when rolled on contacted with other surfaces.

The stabilizer precursor and stabilization activator precursor can be incorporated in photographic emulsions or layers of photographic elements by using any of the photographic techniques commonly used in emulsion making. For example, they can be dissolved in a suitable solvent and added as such or they may be added in the form of a dispersion. Techniques which may be employed in adding the precursor combinations to photographic elements can be similar to the techniques used for adding color couplers to photographic emulsions. Techniques of this type are disclosed, for example, in US. Pat. 2,320,227 and US. Pat. 2,801,171. Solvents or diluents which are miscible with components employed may be utilized to aid in the addition.

An incorporated developer can be applied in a layer of the photographic element. The photographic element can then be developed and the unexposed silver halide thereafter light stabilized or fixed by bringing the photographic element in contact with the combination of stabilizer precursor and stabilization activator precursor in the presence of a heating means such as a heated roller or plate. In such instances, the silver halide emulsion and developer can be present on one support and the stabilizer precursor and stabilization activator precursor may be present on a separate support. It is also possible to have separate layers of silver halide emulsion, developer, stabilization precursor and stabilization activator precursor. It is necessary, however, that the various components of the element be in such positions that desired stabilization will be effected within the above time limits.

Development of the photographic elements of the invention can be effected with conventional developers including phenolic developing agents such as hydroquinone, halogen-substituted hydroquinone such as chlorohydroquinone, bromohydroquinone and dichlorohydroquinone as well as other suitable hydroquinone compounds such as alkyl substituted hydroquinone. Aminophenol developers such as N-methyl-p-aminophenol sulfate can also be employed. 3-pyrazolidone developers such as those dis- The following examples further illustrate the invention.

EXAMPLE 1 3-S-thiuronium propane sulfonate A white paper photographic support having a gelatin layer coating, coated at the rate of 270 ml. per square foot, was coated with a solution, at the rate of 10 grams per square foot, containing the following composition:

Grams/liter t-Butyl hydroquinone 5.0 4 methyl 4 hydroxymethyl l phenyl 3- pyrazolidone 4.5 50.0

3-S-1hiuronium propane sulfanate Guanidiuium trichloroacetate 60.0 27.0

Polyvinyl alcohol Alcohol A 100.0 Water to make 1 liter.

After drying at 40 C. the element was furthercoated in the dark with a slow projection speed silver chloride photographic emulsion at a coverage of 50 mg. per square foot of silver and 57 mg. per square foot of gelatin. Strips of the above prepared light-sensitive coatings were exposed to a line image and a photographic step tablet using conventional tungsten light. The exposed element was then brought into contact with a heated metal block at C. After 2 seconds, a visible image having a maximum density of 1.2 was completely developed and stabilized. Exposure of the thus processed paper to daylight fiuorescent light at 250 foot-candles for 1 hour caused no visible change in the image.

EXAMPLE 2 The process of Example 1 was repeated employing the same compositions as set out in Example 1 with the exception that the coating containing t-butyl hydroquinone and 3-S-thiuronium propane sulfonate was applied to the initial gelatin layer after the slow projection speed silver chloride emulsion was applied. Similar results were obtained to those in Example 1.

EXAMPLE 3 A white paper photographic support was coated at the rate of 10 grams per square foot with a composition comprising:

Grams/ liter Polyvinyl alcohol 48.0 t-Butyl hydroquinone 3 .1

4 methyl 4 hydroxymethyl l phenyl 3- pyrazolidone 3.1 3-S-thiuronium propane sulfonate 31.0 Diguanidinium oxalate 52.0

Ethyl alcohol 100.0 Water to make 1 liter.

A silver chlorobromide emulsion containing 40 mg. per square foot of silver and l20 mg. per square foot of gelatin was coated over the above layer. After exposure, pieces of the coatings were fully developed and stabilized by heating them at 220 C. for 2 seconds.

EXAMPLE 4 Coatings were prepared employing the procedure and compositions of Example 3 with the exception that the diguanidinium oxalate was replaced with one of the alkaline activator precursor componds set out in Table TABLE I.AOTIVATOR PREOURSORS FOR DRY P R 0 E SSIN G Processing Time tempera- Maximum Compounds (see) I ture, 0. density Guanidine salts:

Diguanidinium glutarate 4 190 1. 31 Diguanidinium succinate 2 190 l. 17 Diguanidinium malonate 2 190 1.00 Monoguanidinium malonate. 4 220 0. 94 Monoguanidinium succinate 4 220 1. 1O Diguanidinium adipate 4 190 1. 25 Diguanidinium pimelate 2 100 1. 25 Diguanidinium itaconate. 4 190 1. 23 Malonaltesz I I h 1 N sopropy eye 0 exy amine m onate 4p 220 0. 68 N,N-Diethylethylenediamine bismalonate 4p 220 0. 67 Pyrrolidine malonate. 4p 220 0. 76 Iiperidinium malonat 4p 220 0. 59 Piperazinium malonate 2 190 0. 85 Monoacetamidinium malonate 2 220 1.01 2-Diethylaminoethylamine malonate 2 190 0. 90 Amino acids:

4-Aminobutyric acid" 2 190 1. 05 G-Aminocaproic acid 2 190 1.03 Glycine 4 220 0. 94 DLserine 4 220 0. 81 Miscellaneous:

Oxazolidone 4p 220 0. 80 N-Methyloxazolidone 4p 220 0. 80 Sodium trichloroacetate 2 220 1.00

p indicates partial stabilization at given time and temp.

In each instance, results similar to that achieved in Example 3 were observed. The time suitable for obtaining a developed stabilized image is given in column A of Table I. The temperature employed to achieve the desired image and the maximum density achievable are given respectively in columns B and C of Table I. Hydrazides including benzhydrazide, o-aminobenzhydrazide, isonicotinic acid hydrazide and N-methylpiperidine benzimide employed at temperatures of 190 C. to 220 C. demonstrated similar results.

EXAMPLE 5 The procedure set out in Example 4 was repeated with the exception that the light-sensitive silver halide emulsion was applied to the support below the layer containing the processing chemicals. The results achieved with this procedure were substantially the same as those observed in the prior examples.

EXAMPLE 6 w A coating solution was prepared containing the following components:

Glacial acetic acid ml 4.0 Gelatin ml 20.0 Betaine hydrate g 2.0 1-phenyl-3-pyrazolidone g 0.2 Ascorbic acid g 0 .4 3-S-thiuronium propane sulfonate g 2.0 Water ml 16.0

After mixing the above components, the resulting solution was coated at the thickness of 0.004 inch on a silver chloride emulsion coating on a baryta paper support. The resulting coating was allowed to dry and then a portion thereof was exposed to white light through a step tablet. The exposed coating was then processed by pressing the side of the paper support opposite the emulsion layer against a metal sheet heated at 190 C. for 2 seconds. The processed area of the resulting element was then subjected to 250 foot-candles of illumination for a period of 1 hour. No change in density greater than 0.05 was observed indicating that the resulting coating was stabilized against the effects of light.

In determining the degree of stabilization which is suitable according to the invention, a standard was set whereby the elements produced were exposed to heat for a few seconds and then subsequently exposed to 250 foot-candles of daylight illumination for a period of 1 hour. If the resulting exposed element showed less than 0.05 change in density from the originally unexposed area of the processed element, the element was considered stable and light insensitive.

The following example illustrates that a range of temperatures is suitable for the process of the invention.

EXAMPLE 7 A silver chloride photographic emulsion coating, containing 30 mg. per square foot of silver in gelatin, was applied to a white baryta paper support. The resulting layer was then coated at the rate of 9.5 grams per square foot with a polyvinyl alcohol layer containing the following components:

Grams/ liter Polyvinyl alcohol 20.0 t-Butyl hydroquinone 5.0

4 methyl 4 hydroxymethyl 1 phenyl 3- pyrazolidone 5.0 3-S-thiuronium propane sulfonate 50.0 Diguanidinium oxalate 85.0

Ethyl alcohol 100.0

The following procedure demonstrates the various operable concentration ranges which can be employed in the stabilization process of the invention.

A white baryta paper support was coated with an emulsion containing 23 ml. per square foot of silver. A processing layer was coated over the resulting emulsion layer at the rate of 9.5 grams per square foot. The processing layer was applied as an aqueous solution containing the following components:

Grams/liter Polyvinyl alcohol 20.0 t-Butyl hydroquinone 5.0 4-methyl-4-hydroxymethyl-1- phenyl-3-pyrazolidone 5.0 S-S-thiuronium propane sulfonate 2.560.0 Guanidinium trichloroacetate 60.0 Ethyl alcohol 100.0

Water to make 1 liter.

After drying portions of the resulting element were exposed through a step tablet to tungsten light and then processed by holding the side of the paper support opposite the processing layer in contact with a metal plate for a few seconds at C. Stabilization of the processed image to effects of light was determined by exposing the resulting element to 250 foot-candles of daylight fluorescent light one hour and noting any density change in the areas which originally had no exposure to light. In tests employing the above procedure 0.6, 1.2, 3.6, 7.2, 10.8, and 14.4 moles of 3-S-thiuronium propane sulfonate were employed per mole of silver in the emulsion layer for a series of samples. No density changes greater than 0.05 were observed in the resulting products after heat processing at 2, 4 or 8 seconds. This demonstrates that the activator precursor and stabilizer precursor can be used in a range of proportions.

EXAMPLE '9 A suitable photographic support was coated with a single layer of gelatin at 450 grams per square foot which contained silver halide at 50 mg. per square foot and the following components:

Mg./square foot Chlorohydroquinone 50.0 4,4-dimethyl-1-phenyl-3-pyrazolidone 17.0 2-hydroxyethyl isothiouronium trichloroacetate 850.0 Guanidinium trichloroacetate 100.0

The dried coating was exposed to tungsten light and processed by heating to 160 C. for 4 seconds. The resulting developed and stabilized element had a D of 0.85 with D of less than 0.05 after roomlight exposure for 2 weeks.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A substantially dry photographic silver halide stabilizer precursor composition comprising (a) a silver halide stabilizer precursor which is a sulfur containing compound having the property at temperatures above about 90 C. of forming a compound which complexes with unexposed silver halide forming a mercaptide compound which is more stable to light than said silver halide and (b) a stabilizer activator precursor selected from the group consisting of guanidinium salts, quaternary ammonium malonates, amino acids, heat cleavable organic hydrazide compounds and oxazolidones, said composition having the property of stabilizing said silver halide to light above about 90 C.

2. A substantially dry silver halide stabilizer precursor composition as in claim 1 wherein the said activator precursor is a guanidinium salt of an organic acid.

3. A substantially dry silver halide stabilizer precursor composition as in claim 1 also containing a developer.

4. A substantially dry silver halide stabilizer precursor composition as in claim 1 also containing a binder and a developer.

5. A light sensitive unexposed silver halide emulsion containing therein a silver halide stabilizer precursor which is a sulfur containing compound having the property at temperatures above about 90 C. of forming a compound which complexes with unexposed silver halide forming a mercaptide compound which is more stable to light than said silver halide and a stabilization activator precursor selected from the group consisting of guanidinium salts, quaternary ammonium malonates, amino acids, heat-cleavable organic hydrazide compounds and oxazolidones, said emulsion being insensitive to light at temperatures above about 90 C.

6. A multilayer photographic element comprising a support having thereon at least one light sensitive silver halide emulsion layer and at least one layer containing as a silver halide stabilizer precursor an isothiuronium alkane sulfonate, and as a stabilization activator precursor a guanidinium organic acid salt, said element being insensitive to light at temperatures above about 90 C.

7. A substantially dry developing and stabilization process which comprises heating at a temperature of above about 90 C. for a period of about 1 to about 8 seconds an exposed photographic element comprising a photographic silver halide emulsion, and contiguous to said silver halide an incorporated developer, an isothiuronium alkane sulfonate stabilizer precursor and a guanidinium organic acid salt to develop and stabilize the said element,

8. A substantially dry photographic silver halide stabilizer precursor composition as in claim 1 wherein said stabilizer activator precursor is 6-amino caproic acid.

9. A substantially dry photographic silver halide stabilizer precursor composition as in claim 1 wherein said stabilizer precursor is an isothiuronium alkane sulfonate and said stabilizer activator precursor is an amino acid.

10. A photographic element comprising a support having thereon a coating containing a silver halide stabilizer precursor which is a sulfur containing compound having the property at temperatures above about C. of forming a compound which complexes with unexposed silver halide forming a mercaptide which is more stable to light than said silver halide and a stabilizer activator precursor selected from the group consisting of guanidinium salts, quaternary ammonium malonates, amino acids, heat cleavable organic hydrazide compounds and oxazolidones, said element having the property of being insensitive to light above about 90 C.

11. A multilayer photographic element comprising a support having thereon, a layer containing a silver halide stabilizer precursor which is a sulfur containing compound having the property at temperatures above about 90 C. of forming a compound which complexes with unexposed silver halide forming a mercaptide which is more stable to light than said silver halide and a layer containing a stabilizer activator precursor selected from the group consisting of guanidinium salts, quaternary ammonium malonates, amino acids, heat cleavable organic hydrazide compounds and oxazolidones, said element having the property of being insensitive to light at temperatures above about 90 C.

12. A multilayer photographic element as in claim 10 wherein said stabilizer precursor is an isothiuronium alkane sulfonate and said activator precursor is an amino acid.

13. A substantially dry stabilization process which comprises heating at a temperature above about 90 C. an exposed photographic element comprising a layer containing photographic silver halide, a layer containing a silver halide stabilizer precursor which is a sulfur containing compound having the property at temperatures above about 90 of forming a compound which complexes with unexposed silver halide forming a mercaptide compound which is more stable to light than said silver halide and a layer containing a stabilizer activator precursor selected from the group consisting of guanidinium salts, quaternary ammonium malonates, amino acids, heat cleavable organic hydrazide compounds and oxazolidones, said element having the property of being insensitive to light at temperatures above about 90 C.

14. A substantially dry developing and stabilizing process which comprises heating at a temperature above about 90 C. for a period of about 1 to about 8 seconds an exposed photographic element comprising a photographic silver halide emulsion layer, and contiguous to said silver halide an incorporated developer, an isothiuronium alkane sulfonate stabilizer precursor and an amino acid activator precursor to develop and stabilize said element.

References Cited UNITED STATES PATENTS 3,301,678 l/1967 Humphlett et al. 96-61 NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R. 96109 3x3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. ,2 Dated eptember 29, 1970 Inventofls) nt M. Haist, Wilbert J. Humphlett and Dee L. John It is certified that error appears in the above ide ntified and that said Letters Patent are hereby corrected as shown below z In column 3, line 23 (page 4, line 30 of the application) delete "2-hydroxyethylisothiuronium perchlorate".

In column 3, line 24 (page 4, line 31 of the application) "isothiureido acetic acid" should be moved to the left margin and read ---Isothiureido acetic acid-- In column 3, line 36, (page 5, line 7 of the application) -"B-Caroxgmethylthio-I!phenylpropiophenone methyl" should read ---B-Car oxymethylthio-B-pheny1propi0phenone--; in column 3, lines 37-38 (page 5, lines 8-9 of the application) "on-carbomethoxy-B-(Z-morpholinoethylthio)-B-phenylpropionate hydrochloride" should read ---Methy1 o -Carbomethoxy-B- (2-morpholin0- ethylthio-B-phenylpropionate llydrochloride---.

In column 3, line 73 (page 5, line 43 of the application) "-B-phenylpropionate" should read ---propionate Hydrochloride--- Column 4, line 36 (page 6, line 19 of the application) "sulfanate" should read ---sulfonate--- I w ,s In column 7, line 75 (page 14, line 25 of the' application) "3-pyrazo1idone" should read ---3-Pyrazolidone---.

In column 8, line 23 (page 16, line 11 of the application) "sulfanate" should read ---su1fonate--- I SIGNED mi SEALED M26971 lei-numb.

kaolin? Offioer 

